1. Field
The subject technology relates generally to electronic packaging, and more specifically to methods and apparatus for a chip assembly including a frequency extending device.
2. Background
In optical/electronic and wired/wireless communications, it is increasingly common to communicate using signals with frequencies well into the ranges of a few GHz or tens of GHz. For example, for OC-192/STM-64 optical transmission, the frequency range may be 5 GHz to 15 GHz. For OC-768/STM-256 optical transmission, the frequency range may be, for instance, from 20 GHz to 60 GHz. For the third-generation cellular technology, the frequency range of interest may be between 1.885 GHz and 2.2 GHz or around 5 GHz with the 802.11 standard. As a result, integrated circuits (ICs) suited for these high-speed applications are more in demand now than before.
Before these high-speed ICs can be placed onto a printed wiring board (PWB) or printed circuit board (PCB), they need to be packaged either as a single chip package, a multi chip package, a stacked chip package, or a combination thereof (e.g., a hybrid package or a module). In addition to providing ease of handling and installation, the primary function of a package is one of dimensional transformation. While at the chip level, the input/output (I/O) pad size and spacing are in the order of approximately 3 to 5 mils, the same dimensions at the PWB level are typically 10 to 40 mils. At frequencies below 1 GHz, fanning out using bond wires can generally accomplish this objective. As the operating frequency of the chip approaches 5 GHz or higher, the task of dimensional transformation needs to be accomplished while maintaining the microwave characteristic impedance, typically 50 ohms, of the overall transmission pathway from the chip to the PWB. The bond wires with their inductance and high reactance at these higher frequencies present themselves as discontinuities in a 50 ohm environment, resulting in degraded signal fidelity.